irule issue after upgrade to 12.1.2

Hi all, after we have update the F5 to 12.1.2 one of our VIP containing the irule below enounter intermittent issue. 50% of the traffic was failing at the irule as we run two tcpdump and we could see handshake being establish but we don't see any irule on tcpdump. We already have a F5 case open for more than a week but it seems no one can tell us the root cause. Every other VIP and irules have no issue except this one below.

 

There was no issue the moment we revert back to version 12.1.1. Have anyone else come across this issue ?

 

Current F5 version: 12.1.1 Build 1.0.196 HF1

 

New F5 version: 12.1.2 Build 1.0.27 HF1